*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
:root{
    --clr: #00a2ea;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #223f4d;
}
.navigation{
    position: fixed;
    left: 40px;
    width: 80px;
    padding: 60px 0;
    background: var(--clr);
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 80px;
}
.navigation ul{
    display: flex;
    flex-direction: column;
    gap: 10px;
}
.navigation ul li {
    list-style: none;
    position: relative;
    width: 100%;
    height: 60px;
    padding: 0 10px;
    transition: 0.5s;
}
.navigation ul li::before{
    content: '';
    position: absolute;
    right: 18px;
    top: -13.5px;
    width: 20px;
    height: 20px;
    background: transparent;
    box-shadow: -5px 5px var(--clr);
    z-index: 1;
    border-bottom-left-radius: 20px;
}
.navigation ul li::after{
    content: '';
    position: absolute;
    right: 18.5px;
    bottom: -19px;
    width: 20px;
    height: 20px;
    background: transparent;
    box-shadow: -5px -5px var(--clr);
    z-index: 1;
    border-top-left-radius: 20px;
}
.navigation ul li.active{
    transform: translateX(35px);
}
.navigation ul li a{
    position: relative;
    display: flex;
    align-items: center;
    justify-content: flex-start;
    text-decoration: none;
}
.navigation ul li a .icon{
    position: relative;
    display: block;
    min-width: 65px;
    height: 65px;
    line-height: 75px;
    text-align: center;
    border-radius: 65px;
    background: var(--clr);
    color: #fff;
    font-size: 1.75em;
}
.navigation ul li.active a .icon{
    color: var(--clr);
}
.navigation ul li a .icon::before{
    content: '';
    position: absolute;
    inset: 10px;
    background: #fff;
    border-radius: 50%;
    transition: 0.5s;
    box-shadow: -5px 0 10px rgba(0,0,0,0.25);
    opacity: 0;
}
.navigation ul li.active a .icon::before{
    opacity: 1;
}